Use power of Generics to infer types

underscore/underscore-tests.ts

@@ -3,10 +3,10 @@
 declare var $;
 
 _.each([1, 2, 3], (num) => alert(num.toString()));
-_.each({ one: 1, two: 2, three: 3 }, (value) => alert(value.toString()));
+_.each({ one: 1, two: 2, three: 3 }, (value, key) => alert(value.toString()));
 
 _.map([1, 2, 3], (num) => num * 3);
-_.map({ one: 1, two: 2, three: 3 }, (value: number, key?: string) => value * 3);
+_.map({ one: 1, two: 2, three: 3 }, (value, key) => value * 3);
 
 //var sum = _.reduce([1, 2, 3], (memo, num) => memo + num, 0);	// https://typescript.codeplex.com/workitem/1960
 var sum = _.reduce<number, number>([1, 2, 3], (memo, num) => memo + num, 0);
@@ -16,18 +16,20 @@ var list = [[0, 1], [2, 3], [4, 5]];
 //var flat = _.reduceRight(list, (a, b) => a.concat(b), []);	// https://typescript.codeplex.com/workitem/1960
 var flat = _.reduceRight<number[], number[]>(list, (a, b) => a.concat(b), []);
 
-var even = _.find<number>([1, 2, 3, 4, 5, 6], (num) => num % 2 == 0);
+var even = _.find([1, 2, 3, 4, 5, 6], (num) => num % 2 == 0);
 
-var evens = _.filter<number>([1, 2, 3, 4, 5, 6], (num) => num % 2 == 0);
+var firstCapitalLetter = _.find({ a: 'a', b: 'B', c: 'C', d: 'd' }, l => l === l.toUpperCase());
+
+var evens = _.filter([1, 2, 3, 4, 5, 6], (num) => num % 2 == 0);
+
+var capitalLetters = _.filter({ a: 'a', b: 'B', c: 'C', d: 'd' }, l => l === l.toUpperCase());
 
 var listOfPlays = [{ title: "Cymbeline", author: "Shakespeare", year: 1611 }, { title: "The Tempest", author: "Shakespeare", year: 1611 }, { title: "Other", author: "Not Shakespeare", year: 2012 }];
 _.where(listOfPlays, { author: "Shakespeare", year: 1611 });
 
-var odds = _.reject<number>([1, 2, 3, 4, 5, 6], (num) => num % 2 == 0);
+var odds = _.reject([1, 2, 3, 4, 5, 6], (num) => num % 2 == 0);
 
-//_.every([true, 1, null, 'yes'], _.identity); // https://typescript.codeplex.com/workitem/1960
-_.every<any>([true, 1, null, 'yes'], _.identity);
-_.every<{}>([true, 1, null, 'yes']);
+_.every([true, 1, null, 'yes'], _.identity);
 
 _.any([null, 0, 'yes', false]);
 
@@ -49,7 +51,7 @@ _.sortBy([1, 2, 3, 4, 5, 6], (num) => Math.sin(num));
 
 
 _([1.3, 2.1, 2.4]).groupBy((e) => Math.floor(e));
-_.groupBy([1.3, 2.1, 2.4], (num: number) => Math.floor(num).toString());
+_.groupBy([1.3, 2.1, 2.4], (num) => Math.floor(num).toString());
 _.groupBy(['one', 'two', 'three'], 'length');
 
 _.indexBy(stooges, 'age')['40'].age;
@@ -59,7 +61,7 @@ _(stooges)
 	.indexBy('age')
 	.value()['40'].age;
 
-_.countBy<number>([1, 2, 3, 4, 5], (num) => (num % 2 == 0) ? 'even' : 'odd');
+_.countBy([1, 2, 3, 4, 5], (num) => (num % 2 == 0) ? 'even' : 'odd');
 
 _.shuffle([1, 2, 3, 4, 5, 6]);
 
@@ -87,19 +89,19 @@ _.rest([5, 4, 3, 2, 1]);
 _.compact([0, 1, false, 2, '', 3]);
 
 _.flatten([1, 2, 3, 4]);
-_.flatten([1, <any>[2]]);
+_.flatten([1, [2]]);
 
 // typescript doesn't like the elements being different
-_.flatten([1, [2], <any>[3, <any>[[4]]]]);
-_.flatten([1, [2], <any>[3, <any>[[4]]]], true);
+_.flatten([1, [2], [3, [[4]]]]);
+_.flatten([1, [2], [3, [[4]]]], true);
 _.without([1, 2, 1, 0, 3, 1, 4], 0, 1);
 _.union([1, 2, 3], [101, 2, 1, 10], [2, 1]);
 _.intersection([1, 2, 3], [101, 2, 1, 10], [2, 1]);
 _.difference([1, 2, 3, 4, 5], [5, 2, 10]);
 _.uniq([1, 2, 1, 3, 1, 4]);
 _.zip(['moe', 'larry', 'curly'], [30, 40, 50], [true, false, false]);
-var r = _.object<{ [key: string]: number }>(['moe', 'larry', 'curly'], [30, 40, 50]);
-_.object([[<any>'moe', 30], [<any>'larry', 40], [<any>'curly', 50]]);
+var r = _.object(['moe', 'larry', 'curly'], [30, 40, 50]);
+_.object([['moe', 30], ['larry', 40], ['curly', 50]]);
 _.indexOf([1, 2, 3], 2);
 _.lastIndexOf([1, 2, 3, 1, 2, 3], 2);
 _.sortedIndex([10, 20, 30, 40, 50], 35);
@@ -183,18 +185,15 @@ _.clone(['i', 'am', 'an', 'object!']);
 
 _([1, 2, 3, 4])
 	.chain()
-	.filter((num: number) => {
-		return num % 2 == 0;
-	}).tap(alert)
-	.map((num: number) => {
-		return num * num;
-	})
+	.filter((num) => { return num % 2 == 0; })
+	.tap(alert)
+	.map((num) => { return num * num; })
 	.value();
 
 _.chain([1, 2, 3, 200])
-	.filter(function (num: number) { return num % 2 == 0; })
+	.filter((num) => { return num % 2 == 0; })
 	.tap(alert)
-	.map(function (num: number) { return num * num })
+	.map((num) => { return num * num; })
 	.value();
 
 _.has({ a: 1, b: 2, c: 3 }, "b");
@@ -259,7 +258,7 @@ var moe2 = { name: 'moe' };
 moe2 === _.identity(moe);
 
 var genie;
-var r2 = _.times<number>(3, (n) => { return n * n });
+var r2 = _.times(3, (n) => { return n * n });
 _(3).times(function (n) { genie.grantWishNumber(n); });
 
 _.random(0, 100);
@@ -301,29 +300,27 @@ _(['test', 'test']).pick(['test2', 'test2']);
 //////////////// Chain Tests
 function chain_tests() {
 	// https://typescript.codeplex.com/workitem/1960
-	var numArray: number[] = _.chain([1, 2, 3, 4, 5, 6, 7, 8])
+	var numArray = _.chain([1, 2, 3, 4, 5, 6, 7, 8])
 		.filter(num => num % 2 == 0)
 		.map(num => num * num)
 		.value();
 
-	var strArray: string[] = _([1, 2, 3, 4])
+	var strArray = _([1, 2, 3, 4])
 		.chain()
 		.filter(num => num % 2 == 0)
 		.tap(alert)
 		.map(num => "string" + num)
 		.value();
 
-	var n : number = _.chain([1, 2, 3, 200])
+	var n = _.chain([1, 2, 3, 200])
 		.filter(num => num % 2 == 0)
 		.tap(alert)
 		.map(num => num * num)
 		.max()
 		.value();
 
-	//If using alternate definition of map (~ line 2200), .value returns any
-	//   because.map matches _Chain <number[]> as opposed to _ChainOfArrays <number>, which breaks typing on flatten
-	var hoverOverValueShouldBeNumberNotAny : number = _([1, 2, 3]).chain()
-		.map(num=> [num, num + 1])
+	var hoverOverValueShouldBeNumberNotAny = _([1, 2, 3]).chain()
+		.map(num => [num, num + 1])
 		.flatten()
 		.find(num => num % 2 == 0)
 		.value();

underscore/underscore.d.ts

@@ -23,7 +23,7 @@ declare module _ {
 
 	/**
 	* underscore.js template settings, set templateSettings or pass as an argument
-	* to 'template()' to overide defaults.
+	* to 'template()' to override defaults.
 	**/
 	interface TemplateSettings {
 		/**
@@ -200,7 +200,7 @@ interface UnderscoreStatic {
 
 	/**
 	* The right-associative version of reduce. Delegates to the JavaScript 1.8 version of
-	* reduceRight, if it exists. Foldr is not as useful in JavaScript as it would be in a
+	* reduceRight, if it exists. `foldr` is not as useful in JavaScript as it would be in a
 	* language with lazy evaluation.
 	* @param list Reduces the elements of this array.
 	* @param iterator Reduce iterator function for each element in `list`.
@@ -233,7 +233,15 @@ interface UnderscoreStatic {
 	* @return The first acceptable found element in `list`, if nothing is found undefined/null is returned.
 	**/
 	find<T>(
-		list: _.Collection<T>,
+		list: _.List<T>,
+		iterator: _.ListIterator<T, boolean>,
+		context?: any): T;
+
+	/**
+	* @see _.find
+	**/
+	find<T>(
+		list: _.Dictionary<T>,
 		iterator: _.ListIterator<T, boolean>,
 		context?: any): T;
 
@@ -254,7 +262,15 @@ interface UnderscoreStatic {
 	* @return The filtered list of elements.
 	**/
 	filter<T>(
-		list: _.Collection<T>,
+		list: _.List<T>,
+		iterator: _.ListIterator<T, boolean>,
+		context?: any): T[];
+
+	/**
+	* @see _.filter
+	**/
+	filter<T>(
+		list: _.Dictionary<T>,
 		iterator: _.ListIterator<T, boolean>,
 		context?: any): T[];
 
@@ -297,7 +313,15 @@ interface UnderscoreStatic {
 	* @return The rejected list of elements.
 	**/
 	reject<T>(
-		list: _.Collection<T>,
+		list: _.List<T>,
+		iterator: _.ListIterator<T, boolean>,
+		context?: any): T[];
+
+	/**
+	* @see _.reject
+	**/
+	reject<T>(
+		list: _.Dictionary<T>,
 		iterator: _.ListIterator<T, boolean>,
 		context?: any): T[];
 
@@ -497,7 +521,7 @@ interface UnderscoreStatic {
 	* @return An object with the group names as properties where each property contains the number of elements in that group.
 	**/
 	countBy<T>(
-		list: _.Collection<T>,
+		list: _.List<T>,
 		iterator?: _.ListIterator<T, any>,
 		context?: any): _.Dictionary<number>;
 
@@ -506,7 +530,7 @@ interface UnderscoreStatic {
 	* @param iterator Function name
 	**/
 	countBy<T>(
-		list: _.Collection<T>,
+		list: _.Dictionary<T>,
 		iterator: string,
 		context?: any): _.Dictionary<number>;
 
@@ -603,7 +627,7 @@ interface UnderscoreStatic {
 	/**
 	* Returns everything but the last entry of the array. Especially useful on the arguments object.
 	* Pass n to exclude the last n elements from the result.
-	* @param array Retreive all elements except the last `n`.
+	* @param array Retrieve all elements except the last `n`.
 	* @param n Leaves this many elements behind, optional.
 	* @return Returns everything but the last `n` elements of `array`.
 	**/
@@ -711,7 +735,7 @@ interface UnderscoreStatic {
 	* advance that the array is sorted, passing true for isSorted will run a much faster algorithm. If
 	* you want to compute unique items based on a transformation, pass an iterator function.
 	* @param array Array to remove duplicates from.
-	* @param isSorted True if `array` is already sorted, optiona, default = false.
+	* @param isSorted True if `array` is already sorted, optional, default = false.
 	* @param iterator Transform the elements of `array` before comparisons for uniqueness.
 	* @param context 'this' object in `iterator`, optional.
 	* @return Copy of `array` where all elements are unique.
@@ -817,7 +841,7 @@ interface UnderscoreStatic {
 	* @param array The array to search for the last index of `value`.
 	* @param value The value to search for within `array`.
 	* @param from The starting index for the search, optional.
-	* @return The index of the last occurance of `value` within `array`.
+	* @return The index of the last occurrence of `value` within `array`.
 	**/
 	lastIndexOf<T>(
 		array: _.List<T>,
@@ -918,7 +942,7 @@ interface UnderscoreStatic {
 	/**
 	* Much like setTimeout, invokes function after wait milliseconds. If you pass the optional arguments,
 	* they will be forwarded on to the function when it is invoked.
-	* @param fn Function to delay `waitMS` amount of ms.
+	* @param func Function to delay `waitMS` amount of ms.
 	* @param wait The amount of milliseconds to delay `fn`.
 	* @arguments Additional arguments to pass to `fn`.
 	**/
@@ -954,7 +978,7 @@ interface UnderscoreStatic {
 	* if you call it again any number of times during the wait period, as soon as that period is over.
 	* If you'd like to disable the leading-edge call, pass {leading: false}, and if you'd like to disable
 	* the execution on the trailing-edge, pass {trailing: false}.
-	* @param fn Function to throttle `waitMS` ms.
+	* @param func Function to throttle `waitMS` ms.
 	* @param wait The number of milliseconds to wait before `fn` can be invoked again.
 	* @param options Allows for disabling execution of the throttled function on either the leading or trailing edge.
 	* @return `fn` with a throttle of `wait`.
@@ -1030,14 +1054,14 @@ interface UnderscoreStatic {
 
 	/**
 	* Retrieve all the names of the object's properties.
-	* @param object Retreive the key or property names from this object.
+	* @param object Retrieve the key or property names from this object.
 	* @return List of all the property names on `object`.
 	**/
 	keys(object: any): string[];
 
 	/**
 	* Return all of the values of the object's properties.
-	* @param object Retreive the values of all the properties on this object.
+	* @param object Retrieve the values of all the properties on this object.
 	* @return List of all the values on `object`.
 	**/
 	values(object: any): any[];
@@ -2233,9 +2257,7 @@ interface _Chain<T> {
 	* Wrapped type `any[]`.
 	* @see _.map
 	**/
-	map<TArray>(iterator: (value: T, index: number, list: T[]) => TArray[], context?: any): _ChainOfArrays<TArray>;
-	//Not sure why this won't work, might be a TypeScript error? 
-	//map<TArray>(iterator: _.ListIterator<T, TArray[]>, context?: any): _ChainOfArrays<TArray>;
+	map<TArray>(iterator: _.ListIterator<T, TArray[]>, context?: any): _ChainOfArrays<TArray>;
 
 	/**
 	* Wrapped type `any[]`.
@@ -2247,9 +2269,7 @@ interface _Chain<T> {
 	* Wrapped type `any[]`.
 	* @see _.map
 	**/
-	map<TArray>(iterator: (element: T, key: string, list: any) => TArray[], context?: any): _ChainOfArrays<TArray>;
-	//Not sure why this won't work, might be a TypeScript error?  
-	//map<TArray>(iterator: _.ObjectIterator<T, TArray[]>, context?: any): _ChainOfArrays<TArray>;
+	map<TArray>(iterator: _.ObjectIterator<T, TArray[]>, context?: any): _ChainOfArrays<TArray>;
 
 	/**
 	* Wrapped type `any[]`.